This research will study the effect of various levels of cigarette smoking on the pulmonary clearance of particulates. The pulmonary toxicity of noxious particulates from environmental or occupational sources may be enhanced if normal clearance mechanisms are impaired. Cigarette smoking has been implicated in the impairment of short-term tracheobronchial clearance and has been suspected of impairing long-term alveolar clearance of particles. Magnetopneumography will be used to non-invasively measure both tracheobronchial and long-term alveolar clearance of inert ferrimagnetic particles after a single aerosol inhalation. Eighteen chronic cigarette smokers with normal chest x-rays and spirograms will be studied along with 18 non-smokers. The dose-response characteristics of any alterations in clearance will be explored by dividing the smoking cohort into light, moderate, and heavy smoking groups of 6 each. Magnetopneumography not only allows long-term clearance to be studied in man without large doses of radiotracers, but permits the distribution of dust to be assessed. The method used to measure long-term clearance will distinguish between central lymphatic translocation, pleural lymphatic translocation, and net egress from the lung via the airway or solubilization. Using data from the non-smoking subjects as a baseline, it may be possible to ascertain which aspect of alveolar clearance is impaired by smoking.